Recording material

ABSTRACT

A recording material is described, which comprises a support of paper or of synthetic polymer and an electroconductive layer on at least one side of the support. The surface resistance of this electroconductive layer is not more than 1011 ohms per sq. at a relative humidity of 15 percent. The layer consists or includes a major proportion of a water-soluble polymer resulting from the amino alkylation of polyethyleneimine with an epoxy compound bearing a quaternary ammonium end group. The electroconductive layers may be used as antistatic layers in a photographic silver halide recording material. When covered with a photoconductive coating the electroconductive layer may be used in electrophotographic recording materials. When an insulating layer is applied on the electroconductive layer an electrographic recording material is formed.

Sttes Timmerman et all.

[451 Feb. 4, 1975 1 RECORDING MATERIAL [75] Inventors: Daniel Maurice Timmerman,

Mortsel; Walter Frans De Winter, Berchem, both of Belgium [30] Foreign Application Priority Data Jan. 17, 1972 Great Britain 2134/72 [52] US. Cl ..ll7/20l,117/l38.8 R, 162/138, 162/169, 260/830 R, 260/830 TW [511 int. Cl. B32b 27/00, H011) 1/06 Field of Search ll7/201, 138.8 A;

260/897, 2 EN, 47 EP, 830 R, 830 TW; 162/138, 169; 96/1 R Timmerman 96/67 Dornte 260/2 EN Primary Examiner-Mayer Weinblatt Assistant ExaminerMichael F. Esposito Attorney, Agent, or FirmWil1iam J. Daniel [57] ABSTRACT A recording material is described, which comprises a support of paper or of synthetic polymer and an electroconductive layer on at least one side of the support. The surface resistance of this electroconductive layer is not more than 10 ohms per sq. at a relative humidity of 15 percent. The layer consists or includes a major proportion of a water-soluble polymer resulting from the amino alkylation of polyethyleneimine with an epoxy compound bearing a quaternary ammonium end group.

The electroconductive layers may be used as antistatic layers in a photographic silver halide recording material. When covered with a photoconductive coating the electroconductive layer may be used in electrophotographic recording materials. When an insulating layer is applied on the electroconductive layer an electrographic recording material is formed.

4 Claims, No Drawings RECORDING MATERIAL The invention relates to a recording material comprising a support of paper or of synthetic polymer, at least one surface of which is coated with a layer that may function as an electroconductive or as an antistatic layer.

Electroconductive products are used in recording materials to carry off static charges. For instance, it is known that in normal photographic silver halide emul sion materials the usual synthetic film supports possess the property of being charged electrostatically, whereby the charged films strongly attract the surrounding dust and thereby become soiled at their surface. Moreover, latent discharge images on silver halide emulsions, which are applied to such film support, become visible upon development. Such an electrostatic charging is caused by quickly moving the film support or light-sensitive photographic material during rolling or unrolling in the coating, cutting, or packing machines and by making the film run through the camera and the projector. It is also known that the static charging can be reduced by coating the synthetic resin support with a conductive auxiliary layer.

In other recording materials such as for use in electrostatic printing an electrostatic charge is imparted to paper or other dielectric support in a predetermined pattern. The support is conductive or must be coated with a conductive layer. For instance, in an electrophotographic recording element a photoconductive layer stands in contact with an electroconductive layer or sheet, the latter being present for carrying off the electrostatic charges at the areas of the photoconductive layer undergoing an exposure to light rays.

ln electrographic materials comprising an insulating layer whereon an electrostatic charge pattern is built up by image-wise or record-wise charging, e.g., by means of a modulated electron beam, the conductive element (support or layer) serves to apply a voltage thereto, thus making possible the formation of the electrostatic charge pattern applied to the insulating top layer.

In the following description and claims the general term recording material is intended to include the materials used in photographic processes and in electrographic and electrophotographic processes for which applications the surface resistance of the electroconductive layer must not be higher than 10 ohms per sq. at 15 percent of relative humidity, although according to Nakao, Sakomoto and Katagiri at page l of the Preprints of the Tappi First Reprography Conference at St. Charles, lll., U.S.A., 1971, slight smudging of the back face of the support might already occur at resistance values higher than 4 X ohms/sq.

Electroconductive layers for carrying off electro static charges may also be useful in recording elements wherein photosensitive semiconductor compounds are activated reversely by electromagnetic radiation and wherein the activated patterns provide irreversible images by an oxidation-reduction chemical process.

The invention provides a recording material comprising a support of paper or of synthetic polymer, an electroconductive layer on at least one side of said support, said layer having a surface resistance not more than l0 ohms per sq. at a relative humidity of percent, the said electroconductive layer consisting of or including a major proportion of a water'soluble polymer resulting from the amino alkylation of polyethyleneimine with an epoxy compound bearing a quaternary ammonium end group.

The epoxy compounds bearing a quaternary ammonium end group correspond to the general formula:

wherein:

R represents a branched or unbranched alkylene group having up to 4 carbon atoms,

each of R,, R and R (same or different) represents an alkyl group cntaining up to 4 carbon atoms, a cycloalkyl group or an aralkyl group, or R R and R together with the nitrogen atom represent a heterocyclic amine group such as in pyridine, piperidine, and morpholine, and

X represents an anion, e.g., a halogen atom such as chlorine, bromine, and iodine, a sulphate group, a methylsulphate group, a p-tolysulphonate group, an acetate group and the like.

In fact, the anion X may derive from any suitable acid. For ease of manufacture and especially in view of its better electrical conductivity, the chloride is preferred.

Suitable epoxy compounds bearing a quaternary ammonium end group are, e.g., N-trimethyl-Nglycidylammonium chloride, N-triethyl-N-glycidylammonium chloride and N-triethyl-N-glycidyl-ammonium ptoluene sulphonate.

These epoxy compounds bearing a quaternary ammonium end group can directly be obtained by making an epoxy compound of the formula:

react with a tertiary amine of the formula:

as described by Paquin in Epoxyverbindungen und Epoxyharze, Springer Verlag (1958), p. 202. In these formulae X, R, R R and R have the same significances as indicated above.

Preferably epichlorohydrin is used, although other compounds bearing an epoxy group may also be applied, c.g., l-chloro-3,4-epoxybutane, l-chloro-lmethyl-2,3-epoxypropane, and l-chloro-2-methyl-3,4- epoxybutane.

A preferred tertiary amine is trimethylamine.

The epoxy compounds bearing a quaternary ammonium end group can also be obtained in two reaction steps. In a first step glycidyl amines are formed as described by Gilman and Fullhart in J. Am. Chem. Soc. 71, l478 (1949). For example a secondary amine is made to react with epichlorohydrin:

l\ R]\ I OH NH Cl-GH -CH-CH N-CH CH-CH C1 R 2 2 R I 2 2 O 2 OH tr-CH -CH-CH R 2 2 In a second reaction step the glycidylamine is alkylbelonging to the main polymer chain. Depending on ated to form the epoxy compound bearing a quaternary the ratio of epoxy compound bearing a quaternary amammonium end group: monium end group with respect to the polyethylene- R, R 3,

as described by Burness and Bayer in J. Org. Chem., imine present, the primary amino groups or the primary 28, 228 3-8 1963). and secondary amino groups of the ethyleneimine units The alkylating agent R;,X may be selected from the in the polymer may be amino alkylated partly or comalkyl sulfonates, sulfates, halides or the like. pletely.

The amino slkylation of polyethyleneimine with an The aminoalkylation products of polyethyleneimine epoxy compound bearing a quaternary ammonium end as described in the invention present great advantages. group preferably occurs in aqueous medium at rela- N0 by-products are formed during the reaction, so that tively low temperatures, e.g., at about 50C, the conthe aminoalkylated polyethyleneimine need not be sepm ri f b h l h l i i and epox c arated from the reaction mixture and no further purifipound in the aqueous medium being as high as p055ibie C8110 iS necessary. The reaction mixture can be used At these low temperatures and high polymer and epoxy as Such, Which is y e onomica concemrarions h h d l i f h epoxy group i The electroconductive polymers of the invention d d to a i i comprise recurring units corresponding to the general Further, when a high degree of substitution on the fofmulai amino groups of polyethyleneimine is desired, it is necessary that all the reactive amino groups will be in the -LQH J form of free amino units, and not in form of a salt. 2 2

When the aminoalkylation of polyethyleneimine oc- ATCHZTCHOHTRTIRZ curs in organic medium, e.g., in dimethylformamide, X 5

there is no fear that the epoxy groups might be hydrolysed. Thus the temperature in the reaction mixture can be much higher, e.g. above 100C. 40

It is generally known that the polymerisation of .CH CH NR,

ethyleneimine does not result in a polymer that is completely composed of units having a linear structure, but

wherein A represents a single chemical bond or a group of the formula:

wherein R represents a hydrogen atom or a group of that also a certain degree of branching is found. Acthe formula cording to Zhuk, Gembitskii, and Kargin in Russian N R Chem. Rev., 34 (July 1965) No. 7, page 523, the de- -0H '-0HOH-R- R gree of branching inpolyethylcneimine depends on the R acid concentration and the temperature during polymerisation. This degree of branching may vary be- X, R, R,, R and R,, having the same significances as tween 12 and 38 percent. The formula of polyethylenei di t d b v imine can be represented as follows The molecular weight of the polyethyleneimine before amino alkylation with the epoxy compound bear- CH -CH -N)- CH -CH -NH9 ing a quaternary end group, has little effect on the electroconductive properties of the polymers after amino I 2 alkylation. However, the molecular weight does affect 9 the viscosity of the aqueous coating containing the NH amino alkylated polyethyleneimine. Thus, the choice of the molecular weight of the material to be used is deterwherein, depending on the degree of branching, x is mined by the desired final viscosity. It results from our comprised between 13.6 and 61.3 mole percent and y experiments that polyethyleneimines with molecular b tw 38,7 d 86A, l t, weights ranging from 1,200 to about 50,000 can be As appears from the above formula polyethyleneamino alkylated and that continuous layers of these imine comprises primary and secondary amino groups, amino alkylated polyethyleneimines can be applied to When the polyethyleneimine is made to react with the a upport Without any operational difficulties.

epoxy c mpo d be i a quat n y a mo i end The electroconductivity of the aminoalkylated polyegroup, probably the first substitutions will occur with thyleneimines of the invention is proportional, of one hydrogen atom of the primary amino groups course, to the substitution degree of the amino groups whereby a secondary amino group is formed. Further in the polymer, to the quantity of aminoalkylated polysubstitutions occur on the thus formed secondary mer present per unit of surface, and on the relative huamino groups as well as on the secondary amino groups midity of the layer. It was found that, at 15 percent of relative humidity and about 20C with polyethyleneimine wherein percent of the primary and secondary amino groups have been substituted with N-ethyl-N- glycidylammonium chloride, it was necessary to apply at least 2 g/sq.m to obtain a layer witha surface resistance lower than the l0 ohm/sq. as indicated above. However, when only 1.5 g/sq.m is applied, it is necessary to use polyethyleneimines having a substitution degree of at least 20 percent. Of course the substitution degree may be much higher and amount to about 100 percent whereby a corresponding improvement of the electroconductivity willbe obtained.

The electroconductive polymers of the invention are soluble in water. Their electroconductivity is determined by measuring the surface resistance of layers applied to a support from a 10 percent aqueous solution of the polymer. The resulting layer is dried and conditioned at a specific relative humidity. The surface resistance measurements are performed by means ofa cell, both poles of which have a width of 0.5 cm and are at a distance of 1 cm from each other.

These layers can only be used as an electroconductive layer in an electrographic recording element, when its surface resistance does not exceed well defined limits. The article of Nakao et al., indicated above, cites a value of 4 X 10 ohm/sq. as a limit for smudging of the back face of the paper support. The electroconductivity itself. however, is influenced by the degree of relative humidity. Thus it is advisable to measure a value of surface resistance at percent of relative humidity not higher than 10 oms/sq. In such case a slight backmarking is unavoidable when the relative humidity is very low. The image, however, retains sufficient appeal to be commercially acceptable.

Layers of the electroconductive polymeric materials can be applied by spray, brush, roller, doctor blade, air brush, or wiping techniques to different kinds of supports, e.g., paper. Films of synthetic polymers such as cellulose acetate, polystyrene, polyester, polycarbonate, can also be coated with the electroconductive layers. If necessary, these film supports can be provided previously with a known subbing layer, whereon the electroconductive layer is coated afterwards.

The amount of electroconductive polymeric material applied depends, of course, on the support used. When this support is made of paper and especially ofa highly porous paper stock, more electroconductive polymeric material will have to be applied than in the case of a nonporous synthetic support, e.g., of polyester. In general, however, an amount of 0.5 to 7.5 g/sq.m suffices to provide the layer with a good conductivity.

When paper is used as the support, the electroconductive polymeric materials will also impart electroconductivity when the paper is thoroughly soaked with an aqueous solution of the electroconductive polymeric materials of the invention. After drying of the thus impregnated paper, the electroconductive polymeric material remains dispersed throughout the entire paper base. Electroconductivity may also be conferred to the paper base by adding a sufficient quantity of an aqueous solution of the electroconductive polymeric materials to the papermaking pulp. The amount of incorporated conductive polymer is determined by the required degree of conductivity.

ln addition to the electroconductive polymer of the invention the composition of the electroconductive layer may include stabilizing agents against migrating forces, plasticizers, dispersing agents, pigments, and binders such as gelatin, starch, casein, polyvinyl alcohol and the like. It is obvious that the admixture of such binders determinedly influences the electroconductivity of the layer. Especially polyvinyl alcohol and gelatin are found to lower the electroconductivity of the layer much more than, e.g., starch, as commonly can be found in the literature.

Moreover, the electroconductive polymers of the invention may also be combined with minor amounts, in comparison to the amount of electroconductive polymer present, of inorganic and organic salts, e.g., sodium chloride, sodium sulphate, sodium nitrate. the corresponding potassium and ammonium salts, sodium acetate, citric acid amides, hydroxypropylsucrose monolaurate, etc. These salts are known to be electroconductive. They are inexpensive but have the disadvantage that their electroconductivity is very dependent on the relative humidity. When they are combined with the electroconductive polymers of the invention. the low cost-price of these salts is linked with the excellent electroconductivity at low and high relative humidities of the electroconductive polymers.

When the electroconductive layer of the invention is to be used as an antistatic layer in a photographic silver halide recording material, the electroconductive layer is applied generally to the said sheet or web either on a surface opposite to the surface to which the lightsensitive emulsion layer said polymer is applied, or as an interlayer, i.e., between the support and the lightsensitive emulsion layer or layers.

1f the electroconductive layer is to be used in an electrophotographic recording material, a photoconductive coating is applied to the said polymer layer. This coating is prepared by dispersing or dissolving the photoconductive substance or substances in an organic solution of an insulating binder and by applying the dispersion or solution in the form ofa layer to the electroconductive surfaces.

The electrophotographic recording element prepared with the electroconductive copolymer of the present invention is flexible and possesses a very good mechanical strength. A very good adhesion exists between the paper support and the electroconductive layer.

The electroconductive polymers may be used in combination with coatings of varius inorganic as well as organic photoconductive substances such as those described in the Belgian Pat. No. 587,300 filed Feb. 5, 1960 by Gevaert Photo-Producten N.V., the United Kingdom patent specification Nos. 964,871 filed Feb. 26, 1959, 964,873 and 964,874 both filed Mar. 30, 1960, 964,875 and 964,876 both filed Apr. 21, 1960, 964,877 filed May 2, 1960, 964,879 filed Apr. 26, 1960, 970,937 filed Dec. 9, 1960, 980,879 and 980,880 both filed Feb. 17, 1961 all by Gevaert Photo- Producten N.V., in the German Pat. No. 1,058,836 filed Apr. 14, 1956 by Kalle & Co. A.G. and in the Canadian Pat. No. 568,707 of Kalle and Co. A.G., issued Jan. 6, 1959. These photoconductive substances may be combined with insulating binder agents, known i.a. from the US. Pat. Nos. 2,197,552 of Joseph N. Kuznick, issued Apr. 16, 1940, 2,297,691 of Chester F. Carlson, issued Oct. 6, 1942, 2,485,589 of Frank Graz, issued Oct. 25, 1949, 2,551,582 of Chester F. Carlson, issued May 8, 1951 and 2,599,542 of Chester F. Carlson, issued June 10, 1952, from the United Kingdom patent specification Nos. 566,278 filed .lune 2|, 1943 by Rothschild S. Slathodeon Ltd., 693,1 12 filed May 9, 1950 by Battelle Development Corporation and 700,502 filed Apr. 26, 1949 by Office National DE- tudes et de Recherches Aeronautiques, from the Belgian Pat. Nos. 612,102 filed Dec. 29, 1961 by Gevaert Photo-Producten N.V., 711,376 filed Feb. 28, 1968 by Gevaert-Agfa N.V. and 714,257 filed Apr. 26, 1968 by Gevaert-Agfa N.V., the French Pat. No. 1,485,839 filed June 24, 1966 by Gevaert-Agfa N.V. and the Belgian Pat. No. 683,145 filed June 27, 1966 by Gevaert- Agfa N.V.

Suitable dispersing agents for dispersing photoconductive materials in an aqueous medium are described in the Belgian Pat. No. 703,467 filed Sept. 5, 1967 by Gevaert-Agfa N.V. and as is generally known the photoconductive substances can be spectrally sensitized as described in the Belgian Pat. No. 708,244 filed Dec. 20, 1967 by Gevaert-Agfa N.V. and in the Belgian Pat. No. 714,258 filed Apr. 26, 1968 by Gevaert-Agfa N.V.

The description and claims of the present invention are restricted to the aminoalkylation of polyethyleneimine with epoxy compounds bearing quaternary ammonium end groups. The same aminoalkylation can also be applied to other known polymers containing primary and/or secondary amino groups such as polyvinylamine, polyvinylaniline, polycyclodialkylamines, polyvinylimidazole and polyvinyltetrahydropyrimidine, whereby also electroconductive polymers are obtained.

The invention is illustrated by the following examples.

Example 1 A solution of 43 g of polyethyleneimine in 41 g of water was introduced in a flask provided with a stirrer, a reflux condenser, a dropping funnel, and a thermometer. The solution was heated to 50C.

The polyethyleneimine had a branching degree of about 30 percent, which corresponds with the following general formula wherein .r and y are 42.8 and 57.2 mole percent respectively. A percent by weight aqueous solution of this 10 mole of ethyleneimine in the polymer.

Although the heating was stopped, the temperature in the stirred reaction mixture continued to rise from 50 to 73C as a result of the exothermic reaction between polyethyleneimine and the N-trimethyl-N- glycidylammonium chloride.

The exothermic phase ceased after about 5 minutes. Thereafter the mixture was heated again under stirring to keep the mass at 70C for 5 hours.

The viscous solution was diluted with 200 ml of water and from this solution the addition product of polyethyleneimine and N-trimethylglycidylammonium chloride was isolated by the addition of 1 l of acetone while stirring.

The aqueous acetone solution was decanted and the tacky residue was washed with 0.5 1 of of acetone, dissolved in water and this solution diluted with sufficient water to obtain 350 ml of solution.

Yield: 73 g of modified polyethyleneimine.

it should be kept in mind that these polymers, as a result of their hygroscopicity. at the conditions in which they were dried still contain about 10 percent by weight of water.

Examples 2-10 The process of Example 1 was repeated with the same quantity of polyethyleneimine as starting material and quantities of N-trimethyl-N-glycidylammonium chloride (GAC) varying between 0.1 and 1 mole of ethyleneimine (E1) in the polymer. The results of these processes and of that of Examplel can be found in the following table.

Modified mole of g of GAC in ml of addition yield of polyethy- GAC per water per 43 g of in minumodified leneimine mole of polyethyleneimine tes polymer Example E1 in g 2 0.1 l5.15gin4.5 ml 1 58 1 0.2 30.39 g in 4 ml 1 15 73 3 0.3 45.45 g in 13.5 ml 2 88 4 0.4 60.6 g in 18 m1 5 102 5 0.5 75.75 g in 22.5 ml 15 118.5 6 0.6 90.9 g in 27 ml 17 114 7 0.7 106.1 g in 31.5 ml 149 8 0.8 121.2gin 36 ml 47 164 9 0.9 136.4 gin 40.5 ml 35 179 10 1.0 151.5 g in ml 37 194 us intliented in lixumple l. the hygnmeopieity ot'the modified polymers is very high and in these figures nhout 10 '71 by weight of water is included, even after drying of the modified polymers under reduced pressure to constant weight and in the presence of phosphorus pentoxide.

The modified polyethyleneimines of Examples 1, 3, and 9 were analysed. The following results were found.

It is interesting to compare these figures with those mentioned in Example 5. There we had for the same amount of modified polyethyleneimine per sq.m of pa per: at 50 percent of relative humidity: 18.5 x 10 ohm/sq. at 70 7c of relative humidity: 1.18 X 10 ohm/sq.

Since the aminoalkylated polyethyleneimine of Example had about the same degree of substitution. it is proved that with a chloride anion a much better electroconductivity is obtained, as has already been mentioned above.

mole of GAC Polymer per Surface resistance in ohm/sq.

per mole of sq.m of at C and relative humidity El paper in g Uncoated paper 0 0 42,000,000 21,500 530 Paper coated with unmodified po- 2.0 42,500,000 21,500 193 lyelhyleneimine 1.5* 42,600,000 71,000 386 Paper coated with polymer of Example 2 0.1 2.0 95.000 820 19.3 1.5 425,000 3,540 35.4 1 0.2 2.0 28,300 354 3.86

It appears that the electroconductivity of the amino E l 12 alkylated polyethyleneimine increased with growing content of quaternary ammonium salt, and that the sur- A a of l' fii face resistance of l0 ohm/sq. is not exceeded at any q g l Ei e .53 relative humidity if at least 20 mole percent ofquaterl": 0 LTP e d m 0 g e bur rests ance o ame nar ammomum rou s are resent.

y g p p at 22C and 15 percent relative humidity 3,040 X 10 E l l ohm/sq.

Xamp e at 22C and percent relative humidity 68 X 10 9 g of the same polyethyleneimine as used in Examohm/Sqples ll0, dissolved in 4.6 ml of water were introduced at 22C and 70 percent relative humidity 4.72 X 10 in a flask and the mixture was heated to 40C. ohm/sq.

A solution of 31.3 g of N-triethyl-N- The electroconductive layer is coated with a zinc glycidylammonium p-toluene-sulfonate in 10ml of 50 oxide dispersion prepared as follows. 0.45 liter of cowater was added with stirring. The reaction is not exopolymer of vinyl acetate and dibutyl maleate is diluted thermic. After complete addition the temperature was with 5.6 liters of dichloroethane and then mixed with raised from 40to 70C and thereafter the mixture was 4.2 kg of zinc oxide. The copolymer of vinyl acetate stirred for another hour. The modified polyethyleneand dibutyl maleate comprises approximatively 71 perimine was isolated from the light brown solution by cent by weight of vinyl acetat 2 Pe ent y gh pouring it out in 1.5 1 of acetone. It was then washed of dibutyl maleate and approximatively 0.5 m.eq. of with acetone and dried in vacuo at 40C to constant acetic groups. weight. Yield: 37.3 g of polymer having a nitrogen con- The zinc oxide used is marketed by The Durham tent of 10.38 percent and a sulfone contentof 7.63 per- Chemical Group, Birtley, United Kingdom, under the cent. Accordingly the substitution degree of the pritrade name ELECTROX. The resulting dispersion is mary and secondary amino groups together was 46.5 ground in a sand mill and then admixed with 1.2 liter mole percent. ofthe same copolymer of vinyl acetate and dibutyl mal- When 2.0 g/sq.m of the thus aminoalkylated polyetheate, 1.5 liter of dichloroethane and 67 ml of a 1 peryleneimine was applied from aqueous solution on a cent ethanolic solution of bromophenol blue, with stirpaper base, the layer dried, and the surface resistivity of this layer was measured at 20C, the following results were obtained:

at 50 /t of relative humidity: 1,770 X 10 ohm/sq.

at 70 7! of relative humidity: 101 X 10 ohm/sq.

ring. The dispersion is applied by means of a knife eoater at a ratio of 30 g of zinc oxide per sq.m. and dried.

The material is then treated in a common electrophotographic copying apparatus. If the quality of copies made at different relative humidities is compared, only small differences can be observed. All copies had a good definition.

For comparison a same electrophotographic material was composed, with the difference. however, that the electroconductive layer of amino-alkylated polyethyleneimine was replaced by a layer of unmodified polyethyleneimine. The quality of the copy obtained at a relative humidity of percent and at C was much poorer.

Example 13 A baryta-coated photographic paper was covered with an aqueous solution of the aminoalkylated polyethyleneimine of example 10 at a ratio of 2 g/sq.m (weight of dried material).

The zinc oxide dispersion was then prepared as follows. First 20 g of the copolymer of vinyl acetate and vinyl stearate (85:15 mole percent) were dissolved in 500 ml of ethanol. Then 225 g of photoconductive zinc oxide were added. The resulting mass was ground for 24 hours in a ball mill. Subsequently the following compounds were added with stirring:

2 '71 by weight solution of the copolymer of vinyl acetate and vinyl stearate (85:15 mole /1) in ethanol 10 /1 by weight solution of monobutyldihydrogen phosphate in ethanol 10 solution of succinic acid in dimethylformamide 1 '71 solution of fluoresceine (Colour Index 43.350) in ethanol Example 14 A paper of 60 g/sq.m was impregnated with the aminoalkylated polyethyleneimine of example 10. An aqueous dispersion was then made of 100 g of titanium dioxide, 50 g ofstareh and 150 g of the same aminoalkylated polyethyleneimine. This dispersion was then applied to both sides of the impregnated paper at a ratio of 4 g of solid substance per sq.m. of one side.

50 g of polyvinylbutyral comprising in addition to the vinylbutyral groups approximately 10 percent of vinyl alcohol groups and approximatively 2 percent of vinyl acetate groups were dissolved in 500 ml of ethanol whereto 25 g of barium sulfate were added with thorough stirring. The resulting mixture was ground for 24 hours in a ball mill. The pigment dispersion was then applied to one side of the pretreated paper support at a ratio of 8 g of solid substance per sq.m.

The resulting material can be used for recording intermittent electric charges by means of a series of pins and then developed by means of an electrophoretic developer. When treated in an electrostatic recorder this material offers excellent results even at high recording rates.

Example 15 Strip I Strip 2 Strip 3 water 87.2 g 82.2 g 89.7 g gelatin 3.8 g 3.8 g 3.8 g modified polyethyleneimine 2.6 g 5 2 g l 1 g 20 "/1 aqueous solution of formaldehyde 1.5 g 1.5 g 1.5 g saponine 2.5 g 2.5 g 2.5 g

These coatings were applied in such a ratio that in the three strips after 2 g of gelatin per sq.m. were present.

The following surface resistance values of these layers were measured.

Surface resistance at 20C in 10" ohm/sq.

at l5 /cRH at507z RH M707: RH

Strip 1 4.250.000 2130 30.4 Strip 2 13.300 82 10.6 Strip 3 8,500,000 7100 9.3

An electrophotographic recording material was prepared by coating the electroconductive strip 2 with a solution consisting of:

methylene chloride 45 ml 1 ,E-dichloroethane 45 ml H 1 5 H 0 CH N CH g copoly(vinyl chloride/vinyl acetate/ maleic anhyliride) (mole ratio 86.5/ i 7)- Rhodamine B (0.1. Basic violet '10) (or. a5,17o)

carbon black (average particle sin: 2U nm) 30 g zinc monotridccyl phosphate as dis pcrsing agent l.5 g ISOPAR H (trade name) 750 ml resin solution as described hereinafter I50 g The resin binder solution was prepared by heating 500 g of ALKYDAL L 67 (of Farbenfab'riken Bayer A.G., Leverkusen, W. Germany, for an alkyd resin modified with 67 percent by weight of linseed oil) and 500 ml of white spirit containing ll percent by weight of aromatic compounds at 60C until a clear solution was obtained, and subsequent cooling,

A good transparent copy of the original was obtained.

We claim:

l. A recording material comprising a support of paper or synthetic polymer, an electroconductive layer coated on at least one side of said support, said electroconductive layer having a surface resistance measured at percent of relative humidity lower than 10 ohm/sq., said electroconductive layer consisting of or including a major proportion of a water-soluble polymer resulting from the amino-alkylation of polyethyleneimine with an epoxy compound bearing a quaternary ammonium end group, according to the general formula:

wherein:

R represents a branched or unbranched alkylene group having up to 4 carbon atoms,

each of R R and R (same or different) represents an alkyl group containing up to 4 carbon atoms, a cycloalkyl group or an aralkyl group,

or wherein R R and R together with the nitrogen atom represent a heterocyclic amine group, and

X is an anion.

2. A recording material according to claim 1, wherein said epoxy compound bearing a quaternary ammonium end group is obtained by making an epoxy compound of the formula:

CH CH R X react with a tertiary amine of the formula:

wherein:

R represents a branched or unbranched alkylene group having up to 4 carbon atoms,

each of R,, R and R (same or different) represents an alkyl group containing up to 4 carbon atoms, a cycloalkyl group or an aralkyl group,

or wherein R R and R together with the nitrogen atom represent a heterocyclic amine group, and

X is an anion.

3. A recording material according to claim 2, wherein said epoxy compound bearing a quaternary ammonium compound is N-trimethyl-N- glycidylammonium chloride obtained by making epi chlorohydrin react with trimethylamine.

4. A recording material according to claim 1, wherein the electroconductive layer is formed of 0.5 to

7.5 g/sq.m of said aminoalkylated polyethyleneimine. 1 

2. A recording material according to claim 1, wherein said epoxy compound bearing a quaternary ammonium end group is obtained by making an epoxy compound of the formula:
 3. A recording material according to claim 2, wherein said epoxy compound bearing a quaternary ammonium compound is N-trimethyl-N-glycidylammonium chloride obtained by making epichlorohydrin react with trimethylamine.
 4. A recording material according to claim 1, wherein the electroconductive layer is formed of 0.5 to 7.5 g/sq.m of said aminoalkylated polyethyleneimine. 